title: Synthesis of monomeric Fe(II) and Ru(II) complexes of tetradentate phosphines.
abstract: rac-Bis[{(diphenylphosphino)ethyl}-phenylphosphino]methane (DPPEPM) reacts with iron(II) and ruthenium(II) halides to generate complexes with folded DPPEPM coordination. The paramagnetic, five-coordinate Fe(DPPEPM)Cl(2) (1) in CD(2)Cl(2) features a tridentate binding mode as established by (31)P{(1)H} NMR spectroscopy. Crystal structure analysis of the analogous bromo complex, Fe(DPPEPM)Br(2) (2) revealed a pseudo-octahedral, cis-α geometry at iron with DPPEPM coordinated in a tetradentate fashion. However, in CD(2)Cl(2) solution, the coordination of DPPEPM in 2 is similar to that of 1 in that one of the external phosphorus atoms is dissociated resulting in a mixture of three tridentate complexes. The chloro ruthenium complex cis-Ru(κ(4)-DPPEPM)Cl(2) (3) is obtained from rac-DPPEPM and either [RuCl(2)(COD)](2) [COD = 1,5-cyclooctadiene] or RuCl(2)(PPh(3))(4). The structure of 3 in both the solid state and in CD(2)Cl(2) solution features a folded κ(4)-DPPEPM. This binding mode was also observed in cis-[Fe(κ(4)-DPPEPM)(CH(3)CN)(2)](CF(3)SO(3))(2) (4). Addition of an excess of CO to a methanolic solution of 1 results in the replacement of one of the chloride ions by CO to yield cis-[Fe(κ(4)-DPPEPM)Cl(CO)](Cl) (5). The same reaction in CH(2)Cl(2) produces a mixture of 5 and [Fe(κ(3)-DPPEPM)Cl(2)(CO)] (6) in which one of the internal phosphines has been substituted by CO. Complexes 2, 3, 4, and 5 appear to be the first structurally characterized monometallic complexes of κ(4)-DPPEPM.
authors.affiliation: Ames Laboratory and Chemistry Department, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: Barun
authors.initials: B
authors.lastname: Jana
authors.forename: Arkady
authors.initials: A
authors.lastname: Ellern
authors.forename: Oleg
authors.initials: O
authors.lastname: Pestovsky
authors.forename: Aaron
authors.initials: A
authors.lastname: Sadow
authors.forename: Andreja
authors.initials: A
authors.lastname: Bakac
mesh_terms: D018360:Crystallography, X-Ray; D007501:Iron / Q000737:chemistry*; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D010720:Phosphines / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D010720:Phosphines; D012428:Ruthenium; D007501:Iron